Reproducing apparatus and method, and recording medium

ABSTRACT

A reproducing apparatus and method includes a reproducing unit to reproduce mainstream data and sub audio data separately added in the mainstream data, wherein the reproducing unit comprises a counter used in reproducing the sub audio data. Accordingly, it is possible to more naturally reproduce still image data, such as a browsable slide show, to which sub audio data is additionally included, thus preventing an interruption in reproduction of the sub audio data even during a forward or reverse play.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.10/791,284 filed on Mar. 3, 2004 which claims the benefit of KoreanPatent Application No. 2003-19684 filed on Mar. 28, 2003, Korean PatentApplication No. 2003-82336 filed on Nov. 19, 2003, and U.S. ProvisionalPatent Application No. 60/458,436 filed on Mar. 31, 2003, thedisclosures of which are incorporated herein in their entirety byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a reproducing apparatus and method, andmore particularly, to a reproducing apparatus and method for reproducingstill image data, such as a browsable slide show, to which sub audiodata is separately added, and a recording medium therefor.

2. Description of the Related Art

Because moving picture data is very large, the picture data needs to becompressed using time-space compression to be encoded for easytransmission. In general, to be recorded on an information storagemedium, video data is compressed and encoded under the Motion PictureExpert Groups (MPEG) standards, prescribed by both the InternationalOrganization for Standardization (ISO) and the InternationalElectrotechnical Commission (IEC), whereas audio data is compressedunder the MPEG standards or is converted into digital data using linearPulse Code Modulation (PCM). Time information, necessary forsynchronizing the encoded video data and audio data with each other, isincorporated into system multiplexed data. In this case, the MPEG2standard is also frequently used when encoding data.

The system multiplexing can be performed using packets. For example, asshown in FIG. 1, when multiplexing of video data and audio data, thevideo data and audio data are divided in bitstream packets ofpredetermined lengths, additional information such as a header isincluded in the bitstream packets, and video packets and audio packetsare mixed and transmitted using time-sharing techniques. Therefore, astart of a packet, i.e., a header, includes information indicatingwhether the packet is a video packet or an audio packet.

Meanwhile, time information called time stamp is used in synchronizationbetween audio and video packets according to the MPEG standards.

The time stamp is a type of time management tag that is provided inaccess units for a decoding process required for data reproduction. Thatis, the time stamp is information that specifies when audio or videodata must be decoded and reproduced in access units. There are two typesof time stamps: Presentation Time Stamp (PTS) and Decoding Time Stamp(DTS).

The PTS is time management information of data reproduction selecteddepending on an MPEG coding method adopted, when a System Time Clock(STC), e.g., a reference synchronization signal, which is generated in areference decoder of an MPEG system is equivalent to a PTS, relatedaudio or video data is reproduced and output in access units.

The DTS is time management information of data decoding. The MPEGstandards require the DTS because a sequence of delivering encoded videobitstreams is unique. For example, since an I frame picture and a Pframe picture are delivered as encoded bitstreams before a B framepicture, sequences of decoding and reproducing the I and P framepictures are different from those of decoding and reproducing the Bframe picture. If the PTS and the DTS are not the same, they aresequentially included in the packet data. If they are the same, only thePTS is included in the packet data.

Hereinafter, conventional MPEG encoding and decoding apparatuses will bedescribed with reference to FIGS. 2 through 6.

FIG. 2 illustrates a conventional hierarchical encoding apparatus 200used in MPEG encoding. Referring to FIG. 2, a video encoder 210 receivesand encodes digital video data, and an audio encoder 220 receives andencodes digital audio data.

A first packetizer 230 packetizes the encoded video data output from thevideo encoder 210 by dividing it in predetermined units and generatesPacketized Elementary Streams (PESs). A second packetizer 240 packetizesthe encoded audio data output from the audio encoder 220 by dividing itin predetermined units and generates PESs.

Encoding time information such as the PTS and the DTS may beincorporated into the PES. Such encoding time information is used tosynchronize the PES with other data. In particular, the DTS indicateswhen an image is decoded and the PTS indicates when an image is output.In general, only the PTS is included in the audio data. In this case,the DTS is regarded as being the same as the PTS. After the inclusion ofthe PTS and the DTS, the audio data or video data is packetized in apayload data format.

A program stream multiplexer 250 multiplexes the video PES packetized bythe first packetizer 230 into a program stream (PS). A transport streammultiplexer 260 multiplexes the audio PES packetized by the secondpacketizer 240 into a transport stream (TS). In multiplexing, each PESis divided into predetermined units, identification numbers areallocated to the predetermined units, and the PES is then multiplexed.

The program stream (PS) is made for information storage media andmultiplexed in PS packet units. In a DVD Video standard, arepresentative application for moving image storage media, a PS packetunit of 2048 bytes is used.

The TS is used in an application, such as digital broadcasting, wheredata loss is unavoidable. The TS is multiplexed into TS packet units. ATS packet unit is fixed to be 188 bytes long. Recently, the use of a TSwhen recording digital broadcast data on a storage medium has beenincreased. In this disclosure, the TS is used in multiplexing but the PSalso can be used.

As described above, the TS is packetized data, such as video or audiodata, which is divided in predetermined units so that the data can betransmitted via a satellite, a cable, or a Local Area Network (LAN).Here, the predetermined unit is 188 bytes long, when using the MPEG-2transmission stream according to the ISO/IEC 13818-1 standard, and 53bytes long, when using the Asynchronous Transfer Mode (ATM).

In digital broadcasting, packet data is transmitted at variable timeintervals. The transmitted packet data is input to a buffer of areceiving apparatus having a decoder, decoded by the decoder, andbroadcasted so that a user can view digital broadcasting. The packetdata can be temporarily stored on a recording medium and reproduced at adesired time. In this case, the variable time intervals at which thepacket data was transmitted is significant when the packet data is inputto a decoder of a reproducing apparatus. This is because a transmittingside transmits the packet data to a receiving side while adjusting timeintervals between transmissions of the packet data, in consideration ofthe state of the buffer of the receiving apparatus having the decoder.If the variable time intervals are not adhered to, the buffer at thereceiving apparatus overflows or underflows. Therefore, informationregarding arrival times of the respective packet data transmitted to therecording apparatus is inserted in all packets, and the packet data isreproduced based on the information regarding the arrival times.

As described above, arrival time stamps (ATSs), which are theinformation regarding the arrival times of data, are required for properdata reproduction when packet data transmitted in TS format is recordedon a recording medium and reproduced from the recording medium.

In other words, a recording apparatus receives packet data sent by atransmitting side at particular time intervals and records it on arecording medium. To reproduce the recorded packet data, a counter isrequired to transmit the packet data to a decoder of a reproducingapparatus at the same time intervals as the particular time intervalsused by the transmitting side. The counter operates in response to asystem clock at 90 kHz or 27 kHz, and includes a counter value insertedinto the packet data, the counter being an ATS obtained at an instant oftime a packet is input to the counter. To reproduce the recorded packetdata, the time intervals at which the packet data will be transmitted tothe buffer of the decoder are determined by the counter value includedin the packet data. Such a counter is called an arrival time clock (ATC)counter. That is, an ATS is added into the input packet data based onthe counter value generated by the ATC counter, and the packet data isoutput based on the ATS for data reproduction.

FIG. 3 illustrates a data structure of packet data including ATSsspecifying arrival times of the packet data to a receiving side, and aconnection between the ATSs and data output time when the packet data isreproduced. Referring to FIG. 3, when packet data A, B, C, and D arereceived at arrival times 100, 110, 130, and 150, respectively, arecording apparatus makes ATSs indicating the arrival times 100, 110,130, and 150 and inserts the ATSs into the packet data A, B, C, and D.For data reproduction, the packet data is output and reproduced based onthe ATSs. That is, the packet data A is output at the output time 100,the packet data B is output at the output time 110, the packet data C isoutput at the output time 130, and the packet data D is output at theoutput time 150.

FIG. 4 illustrates a data structure of packet data 400 including ATSswhich is recorded on a recording medium. For convenience, FIG. 4illustrates the packet data 400 to include information, such as an ATS410, a decoding time stamp (DTS) 420, a presentation time stamp (PTS)430, and audio/video (AV) data 440, according to the present invention.

FIG. 5 illustrates a part of a reproducing apparatus 500 that reproducespacket data including ATSs as shown in FIG. 4. The recording apparatus500 includes a disc driving unit 510, a buffer 520, a sourcedepacketizer 530, and an ATC counter 540.

The disc driving unit 510 reads the packet data including the ATSs andtransmits the packet data to the buffer 520.

The buffer 520 receives the packet data including the ATSs and transmitsit to the source depacketizer 530.

The ATC counter 540 is used when a data stream stored in a recordingmedium is transmitted to a decoder (not shown) at intervals of time atwhich the packet data has first been transmitted from a receiving side.The ATC counter 540 operates in response to a system clock at 90 kHz or27 kHz, resets an ATS value, which is obtained at an instant of timewhen a first packet in a TS format is input to the source depacketizer530, as an initial value, and continues counting ATSs of input packets.When an ATS of an input packet is equivalent to a counting valuegenerated by the ATC counter 540, the ATS is removed from the inputpacket and the input packet is sent to the decoder.

In other words, the ATC counter 540 sets the ATS value of the firstinput packet transmitted to the source depacketizer 530 as the initialvalue and begins counting. Next, the source depacketizer 530 checks ATSvalues of next packet data to itself, removes an ATS value from packetdata whose ATS value is equivalent to the counting value generated bythe ATC counter 540, and transmits the packet data to the decoder.

For example, in the case of the packet data of FIG. 3, since a value ofthe ATS of a first packet data is 100, an initial value of the ATCcounter 540 is set as 100 and the ATC counter 540 continues counting.The ATS is removed from the first packet data and the first packet datais transmitted to the decoder. Next, since a value of the ATS of secondpacket data is 110, the source depacketizer 530 removes the ATS from thesecond packet data and transmits the second packet data to the decoder,when a counting value of the ATC counter 540 is 110. The process is alsoapplied to the other packet data in a similar manner.

FIG. 6 is a block diagram of a conventional standard decoder 600 usedfor data synchronization based on encoded time information such as a PTSand a DTS. Referring to FIG. 6, the decoder 600 includes a demultiplexer610, a video decoder 620, a system time clock (STC) counter 630, anaudio decoder 640, and a graphics processor 650.

The demultiplexer 610 demultiplexes multiplexed video packet data, audiopacket data, and sub-picture packet data, and sends the demultiplexedvideo packet data and audio packet data to the video decoder 620 and theaudio decoder 640, respectively. The demultiplexed sub-picture may besubtitle data that is displayed to be overlapped with the video packetdata. In FIG. 6, a decoder that decodes the sub-picture data is notillustrated.

The STC counter 630 operates at 90 KHz or 27 KHz and controls a value ofa packet, which is obtained at an instant of time when the packet isinput to a buffer (not shown) of the decoder, to be equivalent to aprogram clock reference (PCR) value of the packet. The buffertemporarily stores packet data that is output from the demultiplexer 610but has yet to be input to the video decoder 620. The PCR denotes aprogram clock reference that is information used to adjust a value of anSTC counter, which is a reference time value, to a value set by an MPEGdecoding apparatus with video and audio decoders.

A process of decoding packet data including DTSs and PTSs will bedescribed with reference to FIG. 6. First, the demultiplexer 610demultiplexes an input transport packet into the original video packetdata and audio packet data and sends the video packet data and the audiopacket data to the video decoder 620 and the audio decoder 640,respectively.

Next, the STC counter 630 is set based on PCR information (not shown)contained in the packet data. The video packet data is input to thevideo decoder 620 by the set STC counter 630 at a DTS time and decodedby the video decoder 620. Because the audio packet data has only a PTSvalue, the audio packet data is input to the audio decoder 640 at a PTStime, decoded by the audio decoder 640, and output.

Next, the decoded video packet data output from the video decoder 620 isinput to the graphics processor 650 by the STC counter 630 based on thePTS time, processed by the graphics processor 650, and output as videodata.

As described above, the audio and video packet data can be synchronizedwith each other by controlling the decoding and outputting of the audioand video packet data at the PTS time and the DTS time, using a countingvalue generated by the STC counter 630. That is, the audio and videopacket data are decoded and synchronized with each other, in response toa clock generated by the STC counter 630.

In general, there are two applications of still images. First, there isa slide show wherein still images are output at predetermined times.That is, a user reproduces still images using a reverse play where aprevious image is reproduced again or a forward play where reproductionof a current image is skipped and a next image is reproduced. When anSTC value is updated with a new value, images can be sequentiallyreproduced again. If audio data is included in a still image, the audiodata is reproduced in synchronization with a newly updated still image.Thus, the reproduction of the audio data is discontinued, and the audiodata is reproduced again starting from a portion of the audio datacorresponding to a new still image.

Second, there is a browsable slide show. In the browsable slide show,reproduction of audio data must not be discontinued even during thereverse play or the forward play. For instance, the slide show isreproduced as if leafing through the files of a album to view includedphotos. On the other hand, during reproduction of the browsable slideshow with background music, seamless reproduction of the backgroundmusic is required for natural reproduction of still images even if auser selects and reproduces an image preceding or following a currentimage.

Hereinafter, problems with the forward or reverse play of the browsableslide show will be described with reference to FIG. 7. Still images,such as the browsable slide show, are divided into mainstream data andsub audio data. In general, the mainstream data includes video data,audio data, and sub-picture data, but the video data in a browsableslide show application must be understood as still image data excludingaudio data. The sub audio data indicates audio data that is additionallymade separately from the mainstream data and is reproduced as backgroundmusic during reproduction of the still image data.

Referring to FIG. 7, each still image and sub audio data is synchronizedusing PTS information, that is, encoding time information. As datareproduction proceeds, an STC counter value of a decoder (not shown) isincreased and a normal play is performed in accordance with theincreased STC counter value. However, when a user wants to perform thereverse or forward play, the STC counter value is readjusted based on atarget position of the reverse or forward play (e.g., 3000 and 20000).If the STC counter value is updated, the STC counter is reset to 10000to restore both the original still image and the original sub audio,thereby causing an interruption in sub audio data, i.e., backgroundmusic.

As described above, a conventional reproducing apparatus controls both avideo decoder and an audio decoder using an STC counter. Therefore, whenthe conventional reproducing apparatus is used to reproduce still imagesusing an application such as a browsable slide show, it is difficult toprevent an interruption in reproduction of background music when an STCvalue is readjusted during a reverse or forward play. In this case, thebrowsable slide show cannot be reproduced smoothly and might cause aharsh grating noise.

SUMMARY OF THE INVENTION

The present invention provides an apparatus and method for reproducingstill image data, such as a browsable slide show, to which sub audiodata is additionally included, without interrupting reproduction of thesub audio data, i.e., background music, even during a forward or reverseplay, and a recording medium therefor.

According to an aspect of the present invention, there is provided areproducing apparatus comprising a reproducing unit to reproducemainstream data and sub audio data separately added in the mainstreamdata, wherein the reproducing unit comprises a counter used inreproducing the sub audio data.

Additional aspects and/or advantages of the invention will be set forthin part in the description which follows and, in part, will be obviousfrom the description, or may be learned by practice of the invention.

In an aspect of the present invention, the counter includes a sub audioarrival time clock (ATC) counter that is used to depacketize the subaudio data.

In another aspect of the present invention, the counter comprises a subaudio system time clock (STC) counter that is used to decode thedepacketized sub audio data.

In an aspect of the present invention, the mainstream data includesstill image data.

According to another aspect of the present invention, there is provideda reproducing apparatus including a mainstream reproducing unit toreproduce mainstream data including still image data, using a clock formainstream data; and a sub audio reproducing unit to reproduce sub audiodata separately added into the mainstream data, using a clock for subaudio data.

According to another aspect of the present invention, the mainstreamreproducing unit includes a mainstream depacketizer that depacketizesthe mainstream data; and a mainstream ATC counter that provides a clockused in depacketizing the mainstream data with the mainstreamdepacketizer. The sub audio reproducing unit includes a sub audiodepacketizer that depacketizes the sub audio data; and a sub audio ATCcounter that provides a clock used in depacketizing the sub audio datawith the sub audio depacketizer.

According to another aspect of the present invention, the mainstreamreproducing unit includes a mainstream decoder that decodes themainstream data output from the mainstream depacketizer; and amainstream STC counter that provides a clock used in decoding themainstream data with the mainstream decoder. The sub audio reproducingunit includes a sub audio decoder that decodes the sub audio data outputfrom the sub audio depacketizer; and a sub audio STC counter thatprovides a clock used in decoding the sub audio data with the sub audiodecoder.

According to yet another aspect of the present invention, there isprovided a reproducing method comprising reproducing sub audio data,separately added into mainstream data, using a clock for reproducing thesub audio data.

In an aspect of the present invention, the reproducing sub audio dataincludes depacketizing the sub audio data using a clock depacketizingthe sub audio data.

In an aspect of the present invention, the reproducing sub audio dataincludes decoding the sub audio data using a clock decoding thedepacketized sub audio data.

According to still another aspect of the present invention, there isprovided a reproducing method including reproducing mainstream dataincluding still image data using a clock reproducing the mainstreamdata; and reproducing sub audio data, which is separately added in themainstream data, using a clock reproducing the sub audio data.

In an aspect of the present invention reproducing mainstream dataincludes depacketizing the mainstream data using a clock depacketizingthe mainstream data; and decoding the mainstream data using a clockdecoding the depacketized mainstream data.

In an aspect of the present invention reproducing sub audio dataincludes depacketizing the sub audio data using a clock depacketizingthe sub audio data; decoding the sub audio data using a clock decodingthe depacketized sub audio data.

According to still another aspect of the present invention, there isprovided a computer readable recording medium storing a programexecuting a reproducing method, wherein the reproducing method comprisesreproducing sub audio data separately added in mainstream data, using aclock reproducing the sub audio data.

According to still another aspect of the present invention, there isprovided a computer readable recording medium storing a programexecuting a reproducing method, wherein the reproducing method comprisesreproducing mainstream data including still image data using a clockreproducing the mainstream data; and reproducing sub audio dataseparately added into the mainstream data using a clock reproducing thesub audio data.

BRIEF DESCRIPTION OF THE DRAWINGS

These and/or other aspects and advantages of the invention will becomeapparent and more readily appreciated from the following description ofthe embodiments, taken in conjunction with the accompanying drawings ofwhich:

FIG. 1 illustrates a conventional data structure of multiplexed packetdata;

FIG. 2 illustrates a conventional hierarchical encoding apparatus forMPEG encoding;

FIG. 3 illustrates a conventional data structure of packet dataincluding arrival time stamps (ATSs) and a connection between the ATSsand data output time when the packet data is reproduced;

FIG. 4 illustrates a conventional data structure of packet dataincluding time synchronization information;

FIG. 5 illustrates a part of a conventional reproducing apparatus thatreproduces packet data including ATSs;

FIG. 6 is a block diagram of a part of a standard decoder included in aconventional reproducing apparatus;

FIG. 7 illustrates a conventional method of resetting a system timeclock (STC) when reproducing a browsable slide show;

FIG. 8 is a schematic block diagram of a reproducing apparatus accordingto an embodiment of the present invention;

FIG. 9 is a detailed block diagram of the reproducing apparatus of FIG.8;

FIG. 10 is a detailed block diagram of a mainstream decoder shown inFIG. 9; and

FIG. 11 is a flowchart illustrating a method of reproducing still imagedata, according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Reference will now be made in detail to the embodiments of the presentinvention, examples of which are illustrated in the accompanyingdrawings, wherein like reference numerals refer to the like elementsthroughout. The embodiments are described below to explain the presentinvention by referring to the figures.

FIG. 8 is a block diagram illustrating a reproducing apparatus 800according to an embodiment of the present invention. The reproducingapparatus 800 includes a mainstream data reproducing unit 810 and a subaudio data reproducing unit 820.

The mainstream data reproducing unit 810 reproduces mainstream datausing a clock, and includes a mainstream arrival time clock (ATC)counter 905 and a mainstream system time clock (STC) counter 910.

The sub audio data reproducing unit 820 reproduces sub audio data usinga clock, and includes a sub audio ATC counter 906 and a sub audio STCcounter 911.

A structure of the reproducing apparatus 800 will be described in detailwith reference to FIG. 9. As described above, the reproducing apparatus800 reproduces mainstream data using a clock for mainstream data andreproduces sub audio data using a clock for sub audio data. Therefore,even if the clock for mainstream data is adjusted, the clock for subaudio data is not affected by the adjustment, thus enabling seamlessreproduction of sub audio data.

The structure of a reproducing apparatus 900 such as that shown in FIG.8 will now be described with reference to FIG. 9. The reproducingapparatus 900 includes a disc driving unit 901, a mainstream buffer 902,a sub audio buffer 903, a first source depacketizer 904, a mainstreamATC counter 905, a sub audio ATC counter 906, a second sourcedepacketizer 907, a demultiplexer 908, a mainstream decoder 909, amainstream STC counter 910, a sub audio STC counter 911, a sub audiodecoder 912, and a graphics processor 913.

The disc driving unit 901 reads packet data including arrival timestamps (ATSs) from a recording medium 914, transmits mainstream packetdata including still image data from the packet data to the mainstreambuffer 902, and transmits sub audio packet data to the sub audio buffer903.

The first source depacketizer 904 receives the mainstream packet datafrom the mainstream buffer 902, depacketizes the mainstream packet data,and sends the depacketized mainstream data to the demultiplexer 908.More specifically, the first source depacketizer 904 transmits thedepacketized mainstream data, from which the ATSs are detached, to thedemultiplexer 908 at predetermined time intervals, based on ATSinformation added to the mainstream packet data by the mainstream ATCcounter 905.

The mainstream ATC counter 905 controls the first source depacketizer904 to send the depacketized mainstream data to the demultiplexer 908 atthe predetermined time intervals. More specifically, the mainstream ATCcounter 905 is initialized based on an ATS value of the first mainstreampacket data input to the first source depacketizer 904, and startscounting at the same time. When a counting value of the mainstream ATCcounter 905 is equivalent to a value of an ATS of a second mainstreampacket data input to the first source depacketizer 904, the first sourcedepacketizer 904 depacketizes the second mainstream packet data andsends the depacketized mainstream data to the demultiplexer 908.

The operations of the second source depacketizer 907 and the sub audioATC counter 906 are the same as those of the first source depacketizer904 and the mainstream ATC counter 905, respectively.

The second source depacketizer 907 receives a sub audio packet data fromthe sub audio buffer 903, depacketizes the sub audio packet data, andoutputs the depacketized sub audio data to the sub audio decoder 912.More specifically, the second source depacketizer 907 outputs thedepacketized sub audio data, from which ATSs are detached, atpredetermined time intervals, based on ATS information added to the subaudio packet data by the sub audio ATC counter 906.

The sub audio ATC counter 906 controls the second source depacketizer907 to output the sub audio packet data at the predetermined timeintervals. More specifically, the sub audio ATC counter 906 isinitialized based on an ATS value of a first sub audio packet data inputto the second source depacketizer 907, and the sub audio ATC counter 906starts counting at the same time. When a counting value of the sub audioATC counter 906 is equivalent to a value of an ATS added to a second subaudio packet data input to the second source depacketizer 907, thesecond source depacketizer 907 depacketizes the second sub audio packetdata and outputs the depacketized sub audio data. The depacketized subaudio data output from the second source depacketizer 907 may be sent toa buffer (not shown).

The demultiplexer 908 demultiplexes the depacketized mainstream datacontaining a decoding time stamp (DTS) and presentation time stamp (PTS)and sends the demultiplexed data to the mainstream decoder 909. Thedemultiplexed mainstream data output from the demultiplexer 908 isbuffered by a decoding buffer (not shown) before the demultiplexedmainstream data is input to the mainstream decoder 909.

The mainstream STC counter 910 operates at 90 kHz or 27 MHz. Themainstream STC counter 910 is set based on program clock reference (PCR)information (not shown) contained in the packet data, and controls avalue of the packet data obtained at an instant of time when the packetdata is input to the decoding buffer based on the PCR value contained inthe packet data.

The set mainstream STC counter 910 controls the demultiplexed mainstreamdata to be input to the mainstream decoder 909 at a DTS time specifiedin the DTS information and decoded by the mainstream decoder 909.

The decoded mainstream data output from the mainstream decoder 909 isinput to the graphics processor 913 at a PTS time specified in the PTSinformation. The decoded mainstream data is processed by the graphicsprocessor 913, and output.

The operation of the mainstream STC counter 910 is similar to that ofthe mainstream ATC counter 905. That is, the mainstream STC counter 910is initialized based on the PCR information and starts counting at thesame time.

The mainstream decoder 909 decodes the demultiplexed mainstream data andtransmits the decoded result to the graphics processor 913 when acounting value of the mainstream STC counter 910 is equivalent to avalue of a DTS of packet data. Also, the graphics processor 913processes the received decoding result and outputs a processing resultto a screen (not shown) when the counting value of the mainstream STCcounter 910 is equivalent to a value of the PTS contained in the packetdata.

The operations of the sub audio STC counter 911 and the sub audiodecoder 912 are similar to those of the mainstream STC counter 910 andthe mainstream decoder 909.

The sub audio STC counter 911 operates at 90 kHz or 27 MHz, and controlsa value of the depacketized sub audio data that is input to a decodingbuffer, which temporarily stores data, based on a PCR value contained inthe packet data.

The set sub audio STC counter 911 controls the depacketized sub audiodata to be input to the sub audio decoder 912 at a PTS time specified inthe PTS information and decoded by the sub audio decoder 912.

The operation of the sub audio STC counter 911 is similar to that of themainstream STC counter 910. That is, the sub audio STC counter 911 isinitialized based on PCR information contained in the packet data andstarts counting at the same time.

The sub audio decoder 912 decodes the depacketized sub audio data when acounting value of the sub audio STC counter 911 is equal to a PTS valueincluded in the packet data. The sub audio data is decoded and output tothe screen without performing additional processing on the sub audiodata.

FIG. 10 illustrates in detail the mainstream decoder 909 of FIG. 9. Themainstream decoder 909 includes an audio decoder 1 that decodes audiodata, a sub picture decoder 2 that decodes sub picture data, and a videodecoder 3 that decodes video data. Mainstream data of an application ofstill image data, such as a browsable slide show, may include videodata, i.e., still image data, and sub picture data such as subtitles,but the mainstream data does not include audio data. Accordingly, theaudio decoder 1 is not used in the browsable slide show application.

The audio decoder 1, the sub picture decoder 2, and the video decoder 3decode audio data, sub picture data, and video data respectively, basedon a counting value of the mainstream STC counter 910 of FIG. 9.

FIG. 11 is a flowchart illustrating a method of reproducing stillpicture data with separately added sub-audio data, according to anembodiment of the present invention. Referring to FIGS. 9 and 11, thedisc driving unit 901 reads packet data from the recording medium 914(operation 1100).

Mainstream data of the read packet data, which includes still imagedata, is stored in the mainstream buffer 902 and sub audio data of theread packet data is stored in the sub audio buffer 903 (operation 1110).

Next, the first source depacketizer 904 depacketizes the mainstream databased on a counting value of the mainstream ATC counter 905, and thesecond source depacketizer 907 depacketizes the sub audio data based ona counting value of the sub audio ATC counter 906 (operation 1120).

Next, the demultiplexer 908 demultiplexes the mainstream datadepacketized by the first source depacketizer 904 (operation 1130).

Next, the mainstream decoder 909 decodes the demultiplexed mainstreamdata based on a counting value of the mainstream STC counter 910, andthe sub audio decoder 912 decodes the depacketized sub audio data basedon a counting value of the sub audio STC counter 911 (operation 1140).

Next, the decoded mainstream data and sub audio data are output(operation 1150).

The method of FIG. 11 can be embodied as a computer readable code in acomputer readable medium. Here, the computer readable medium may be anyrecording apparatus capable of storing data that is read by a computersystem, e.g., a read-only memory (ROM), a random access memory (RAM), acompact disc (CD)-ROM, a magnetic tape, a floppy disk, an optical datastorage device, and so on. Also, the computer readable medium may be acarrier wave that transmits data via the Internet, for example. Thecomputer readable recording medium can be distributed among computersystems that are interconnected through a network, and the presentinvention may be stored and implemented as a computer readable code inthe distributed system.

As described above, according to the present invention, it is possibleto more naturally reproduce still image data, such as a browsable slideshow, to which sub audio data is separately added, using a clock formainstream data and a clock for sub audio data, thereby preventing aninterruption in reproduction of sub audio data such as background musiceven during a forward or reverse play.

Although a few embodiments of the present invention have been shown anddescribed, it would be appreciated by those skilled in the art thatchanges may be made in this embodiment without departing from theprinciples and spirit of the invention, the scope of which is defined inthe claims and their equivalents.

1. A reproducing apparatus, comprising: a mainstream data reproducingunit configured to reproduce mainstream data using a mainstream arrivaltime clock which is configured to be used to depacketize the mainstreamdata and a mainstream system time clock which is configured to be usedto decode the depacketized mainstream data; and an audio datareproducing unit configured to reproduce audio data corresponding to themainstream data, using an audio arrival time clock which is configuredto be used to depacketize the audio data and is independent of themainstream arrival time clock and an audio system time clock which isconfigured to be used to decode the depacketized audio data and isindependent of the mainstream system time clock, wherein the mainstreamdata reproducing unit and the audio data reproducing unit areindependent such that the mainstream data is changeable by a user, whilenot interrupting the audio presentation, and wherein the mainstreamarrival time clock is initialized based on an arrival time stamp valueof a first packet of the mainstream data, and the audio arrival timeclock is initialized based on an arrival time stamp value of a firstpacket of the audio data.
 2. The apparatus of claim 1, wherein themainstream data is changeable by the user using a skip next operation ora skip back operation.
 3. The apparatus of claim 1, wherein: themainstream data reproducing unit comprises: a mainstream data decoderconfigured to decode the mainstream data; and the mainstream System TimeClock configured to provide a clock used in decoding the mainstream datawith the mainstream data decoder; and the audio reproducing unitcomprises: an audio data decoder configured to decode the audio data;and the audio System Time Clock configured to provide a clock used indecoding the audio data with the audio decoder.
 4. A reproducing method,comprising: reproducing mainstream data using a mainstream arrival timeclock which is configured to be used to depacketize the mainstream dataand a mainstream system time clock which is configured to be used todecode the depacketized mainstream data; and reproducing audio datacorresponding to the mainstream data, using an audio arrival time clockwhich is configured to be used to depacketize the audio data and isindependent of the mainstream arrival time clock and an audio systemtime clock which is configured to be used to decode the depacketizedaudio data and is independent of the mainstream system time clock,wherein the mainstream data reproducing process and the audio datareproducing process are independent such that the mainstream data ischangeable by a user, while not interrupting the audio presentation,wherein the mainstream arrival time clock is initialized based on anarrival time stamp value of a first packet of the mainstream data, andthe audio arrival time clock is initialized based on an arrival timestamp value of a first packet of the audio data.
 5. The method of claim4, wherein the mainstream data is changeable by a user using a skip nextoperation or a skip back operation.
 6. A reproducing apparatus,comprising: a mainstream data reproducing unit configured to reproducemainstream data using a mainstream arrival time clock which isconfigured to be used to depacketize the mainstream data and amainstream system time clock which is configured to be used to decodethe depacketized mainstream data; and an audio data reproducing unitconfigured to reproduce audio data corresponding to the mainstream data,using an audio arrival time clock which is configured to be used todepacketize the audio data and is independent of the mainstream arrivaltime clock and an audio system time clock which is configured to be usedto decode the depacketized audio data and is independent of themainstream system time clock, wherein the mainstream data reproducingunit and the audio data reproducing unit are independent such that themainstream data is changeable by a user, while not interrupting theaudio presentation, and wherein the mainstream system time clock isinitialized based on a time value of a predetermined packet of themainstream data, and the audio system time clock is initialized based ona time value of a predetermined packet of the audio data.
 7. Thereproducing apparatus of claim 6, wherein the time value is a programclock reference.